I mainly use Danville's which I buy mainly on Ebay even though I've a couple of other Brands of Thread.
Most Tyers at some time has broken thread which I have found mainly due to Rough &/or Cracked Fingers.
Brian.

All I know is from my personal experience. I have countless spools of Uni 8/0 and it is good but I find I will get in to sections of the thread where it breaks easily when tying, other sections strong and don't break as easily. I have tied down to size 22 flies with Uni 8/0 no problem.

I just started buying / using Veevus 12/0 and for me it is hands down better. Have tied down to a 26 with it and it is great. Veevus is my new go to fly tying thread. To me Veevus is a little thinner, stronger and more consistent .

Veevus is stronger for its size, I am certain of that. Chris Helm's excellent list of threads included an ESTIMATE of Veevus denier based on its breaking strength. He could not get the actual denier from the manufacturer. Any conclusions based on Helm's list of denier values for Veevus thread are misleading.

Made of the same material as some of the comparable threads, Veevus thread construction appears empirically stronger in use. I find the Veevus 12/0 to be stronger than the Uni 8/0 in tying the same flies with the same Tiemco ceramic bobbin and the same materials.

My guess is when the actual denier values for Veevus are released, we will find it to be a denser thread with greater grams per 9000 meters. Veevus 12/0 is definitely thinner than Uni 8/0, based on the visual evidence "on the hook."

Veevus 12/0 is my new "go to" thread, but I still like and use the Uni 8/0. It grips well, slightly better than Veevus with slippery materials. I find that Veevus 12/0 requires one more turn to hold something slick, like wire or like the sulky metallic black on a Tungsten Torpedo, for example, than does the Uni. That extra turn still keeps things slim.

Also, I wax my threads with a fantastic wax from Great Feathers Fly shop made to old recipes. The Uni 8/0 waxes nicely, while the Veevus splits ever so slightly while waxing, temporarily, without fraying. Davie McPhail and Davy Wotton taught me to wax my threads, and it helps provides a sure grip on materials as well as protecting silk threads from rot.

If I am ever good enough to tie as small as some of the experienced hands here, in the 20's of hook size (whew that is small) , it will be Veevus thread I take to that test of eyes, hands and nerves.

Well a special thanks to PlanetTrout for getting me hooked on the Kool aid and to my wife for humoring a few more debits to the acct.

I am so hooked on Veevus I now have 9 spools of 12/0 4 spools of 16/0 and one spool of 14/0 just because I couldn't find the brown I wanted in 12/0. Of course I had to buy 10 spools and two additional bobbins from NorVise to hold them all